No, it's not a seafood. And it's not a pork or chicken dish, the second and third most popular. But it does come from the fourth and most expensive meat. We're talking about cow's tongue, gyutan (gyu meaning cow and tan borrowed from the English word tongue).
Its Japanese origins stem from 1948 when a Sendai restaurant owner, trying to survive after the war, started using the kitchen discards of the American occupation forces; his particular focus was the tongue of the cow. Now it is so popular, however, that there are restaurants in Tokyo and Sendai that are dedicated cow tongue restaurants, serving nothing but gyutan, each, of course, offering a couple dozen different exotic preparations. And this culinary capital takes its food preparation to a high art, so you can imagine the creative flavoring and cooking methods they draw on.
This is a perfect illustration of the way Japan adopts things from other cultures, then adapts them to their own needs or taste. Some very common examples are the writing system from the Chinese (they created two alphabets to adapt the Chinese characters to Japanese language), sports (baseball is very popular in Japan and the best outcome is a tie!), other foods (like tempura from the Portuguese) and the political system (its democracy is like no other). Even by adopting Western dress, it gives the deceptive impression that Japanese businessmen in Western suits will do business the same way Western businessmen do. But the reality is that business in Japan is conducted with Japanese sensibly and customs.
Back to gyutan, while grilled is the traditional preparation, some current variations include tongue salad, tongue sashimi, tongue ramen, tongue katsu (breaded cutlet), roasted tongue, mashed tongue, fried tongue, salted tongue, tongue potato chips, tongue sauce covered tofu, smoked tongue, barbecued tongue, fried eggs blended with tongue, and even tongue ice cream!
There are thousands of restaurants now serving gyutan, ranging from the very upscale to fast food restaurants, and even two chains (the most popular being Rikyu and Kisuke).
People describe it as being taihen oishii (very delicious): tender, with a slightly crunchy texture and succulent flavors.
So, on your next trip to Japan are you ready for some good old America beef - tongue? If you didn't know better, you may well find yourself licking your lips while eating tongue potato chips saying, "Where's the beef?"